This invention relates to blood fractions and more particularly to a method for the preparation of a serum albumin fraction in high yield and purity.
Albumin constitutes the largest fraction of blood plasma and finds wide use in medical therapy such as in cases of shock and as a plasma extender.
The fractionation of blood by various procedures to obtain albumin and recover other separated components is an established practice. A principal albumin fraction of commerce known as normal serum albumin is an osmotically stable solution of a highly purified plasma fraction containing at least 96% albumin. Its availability has been made possible largely through the work of Cohn and his associates at the Harvard Medical School and its preparation is described in U.S. Pat. Nos. 2,390,074 and 2,469,193; J. Amer. Chem. Soc. 68, 469-75 (1946); Kirk-Othmer, Encyl. of Chem. Tech., 3, 584-88 (2d. ed. 1964). The current method of choice in the United States for the preparation of normal serum albumin is the so-called Method 6 of Cohn.
Another principal albumin fraction of commerce is the so-called plasma protein fraction (PPF) which is a solution of a plasma fraction containing at least 83% albumin together with a mixture of not more than 17% .alpha.- and .beta.- globulins. The current method of choice in the United States for the production of PPF is that of Hink as described in U.S. Pat. No. 2,958,628 and Vox Sang.2, 174 (1957).
The foregoing procedures for obtaining the more highly concentrated normal serum albumin and the less concentrated PPF make use of cold ethanol as a precipitating agent in the fractionation schemes. Various other known procedures for the preparation of albumin fractions make use of other precipitating agents such as ether, methanol or ammonium sulfate salt, or involve adsorption on gels or ion exchange chromatography.
More recently, various polymeric materials have been developed for the fractionation of blood, including the separation of albumin, for example, polyethylene glycol (PEG, Carbowax) as described in U.S. Pat. No. 3,415,804; copolymers of ethylene oxide and polyoxypropylene polymer (Pluronics) as disclosed in U.S. Pat. No. 3,850,903 and German Offenlegunsschrift 2,403,065; and certain unique polyelectrolytes such as ethylene/maleic anhydride, cross-linked copolymer derivatives defined in U.S. Pat. Nos. 3,554,985 and 3,555,001. An advantage of the use of these polymeric materials is that they can be employed at normal room temperature and thus avoid the cold temperature requirements of the Cohn ethanol fractionation procedure.
Still another method of obtaining a purified serum albumin involves the selective denaturation of serum globulins without denaturation of the serum albumin by heating in the presence of caprylate or other fatty acid anion stabilizers as described in U.S. Pat. Nos. 2,705,230 and 2,765,299; J. Biol. Chem. 162, 181-98 (1946); and Blut 30, 121-134 (1975). While useful for the preparation of PPF type albumin fractions, this method is not generally suitable for the preparation of highly purified serum albumin in high yield without destruction of valuable gamma globulins. It is usually carried out as a pasteurization step to provide a virus-free albumin product.